In Safari 5.1 or later:

In Safari 5.0 or earlier:

In the Preferences window, click Security.

Click the Show Cookies button.

Click the Remove All button, then click Done.

Firefox

Close all Firefox windows.

Open a new Firefox session.

Open the Clear Recent History window.In Windows: Click History > Clear Recent History.... (If you do not see "History," press the Alt key to show the menu bar.)In Mac OS X: Click Firefox > History > Clear Recent History....

Click the drop-down menu next to Time range to clear and choose Everything.

Click the arrow next to Details and select both Cookies and Cache.

Click the Clear Now button.

Note: This may take a few minutes to process. Please wait for the files to delete before you continue.